Family studies indicate a possible linkage between the q13.2 region of chromosome 19 and Alzheimer's disease (AD). An isoform of apolipoprotein E, whose gene maps in this region, is more frequent in AD. In this study, we investigated the possible association of a genetic polymorphism of the apolipoprotein E gene with late-onset AD. We compared apolipoprotein E polymorphism distribution between patients with sporadic late-onset AD (n = 36) and controls of the same age (n = 38). Individuals carrying at least one e4 allele were present in 41.7% of the patients, compared with only 10.5% of the controls (p < 0.001). This result indicates an association between late-onset AD and the 19q13.2 region containing the apolipoprotein E gene locus.